This invention relates generally to apparatus for preventing unauthorized use of machinery (such as motor vehicles) and more particularly to such apparatus that employ ignition circuit interrupt systems to prevent such unauthorized use.
Numerous systems and methods have been suggested in the past for deenergizing an ignition circuit of a motor vehicle and sounding alarms upon an unauthorized attempt to move the vehicle. The designs of many such systems have involved the use of energized relays or solenoids to complete vital links in the ignition circuit. That is, when power has been removed from these relays, or solenoids, these links have been broken and internal combustion engines energized thereby have stopped running. Such systems have had the disadvantage of creating an obvious danger in that, if such a device should experience failure during operation of a vehicle equipped therewith, engine failure would automatically result, thereby endangering lives of a vehicle operator, passengers and motorists of other cars.
Other designs have required operators to flip switches prior to leaving their vehicles in order to arm devices so that unauthorized operators, who do not know how to disarm the devices cannot thereafter use the vehicles. Such a design places responsibility on the operator to actively take part in setting it. Unfortunately, many operators forget to manipulate the switches or consciously decide not to manipulate them so that their vehicles remain unprotected. In addition, some such devices suffer from an additional drawback in that if the switches are inadvertently manipulated during vehicle operation automatic engine failure immediately follows, thereby also creating life threatening situations.
Still other designs require operators to insert keys into ignition switches and then perform acts or series of acts, to disarm devices prior to attempting engine starts. Depending on particular designs, such actions required prior to engine starts can be awkward and frustrating for operators. Thus, these designs often lead to operators disabling the devices in order to avoid the inconveniences involved in using them.
Most anti-theft devices do not allow operators to remove keys from ignition switches while still allowing engines to warm up.
There are anti-theft devices that exist which interrupt, or drain, normal current flow to vehicle ignition coils. Unfortunately, many of these devices are incompatible with computer controlled ignition systems often used in automobiles today. In this regard, it is unknown what effect such devices have on ignition computers which attempt to compensate for sensed faults.
Some prior-art anti-theft devices are designed to isolate starters. Intelligent thieves can easily recognize this as not being a likely characteristic of modern vehicles and are thereby "tipped of" to search for and disarm such devices.
For all of the above reasons, it is an object of this invention to provide an apparatus for preventing unauthorized use of machinery (such as motor vehicles) which:
operates in a fail-safe mode so that it will not interfere with a vehicle's ignition system during normal operation if it or its wiring fails; PA1 employs a totally passive reset capability; PA1 cannot interfere with normal machinery operation upon purposeful or inadvertent activation of a switch; PA1 allows an internal-combustion engine to be started normally and then disarmed at an operator's leisure; PA1 provides a false sense of accomplishment to a potential thief for thereby denying him the knowledge that an anti-theft device has been installed; PA1 allows an authorized operator of a vehicle to leave the vehicle idling without leaving the ignition key in the vehicle, but with the anti-theft device armed; PA1 can be used during warm-up operations; PA1 is safe for use on all types of ignition circuits, including computer-controlled, electronic, and conventional ignition circuits; PA1 alerts an authorized owner of an attempted theft or unauthorized used; PA1 is difficult to disable and does not alert thieves of its existence; PA1 does not drain a battery current; PA1 can be bypassed to allow authorized use by third parties (such as maintenance personnel, valet parking attendants, etc.) without disclosing hidden switch positions; PA1 allows stalled engine restarts without having to reset the device; and PA1 is economical to manufacture, easy and economical to install and is convenient and safe for an owner to operate.